RRFM 2009 Transactions - European Nuclear Society

(a)
Weight fraction (%)
100
90
80
70
60
50
40
30
20
10
U 3 Si 5 pure phase, probably due to some Al substitution) is found in coexistence with an
highly Si enriched U(Al,Si) 3 phase (according to its cell parameter [13]). The thin intermediate
layer shown by SEM+EDS examinations is not clearly evidenced by µ-XRD measurements,
perhaps because it just corresponds to a transition zone, with no specific "signature" in terms
of phases. Close to the Al side, as in type 1 ILs, U(Al,Si) 3 + UMo 2 Al 20 phases are present, the
Si enrichment of the U(Al,Si) 3 phase being greater than that found in type 1 ILs. Some α-U is
also evidenced in U-Mo : its presence was not systematically noticed and could be linked to
a local destabilisation of γU-Mo.
(b)
Al U-Mo Al +Si
Al + Si
UAl3
U(Al,Si)3
Al
UMo2Al20
U6Mo4Al43
UMo7
UC
0
0 100 200 300 400 500 600
Vertical position (µm)
Figure 5 : µ-XRD analysis of an U-Mo7/Al-Si2 diffusion couple.
(a) Major phases distribution throughout the IL, (b) simplified summary of the results
Al
U(Al,Si) 3 (a moy = 4.23 Å 17 at% Si)
+ UMo 2 Al 20
UAl 3 (a moy = 4.27 Å)
+ U 6 Mo 4 Al 43
γU-Mo7 + traces (UC…)
(a)
Weight fraction (%)
100
90
80
70
60
50
40
30
Al
U(Al,Si)3
Al
UMo2Al20
U3Si5
UMo7
UC
Ualpha
U-Mo
(b)
Al + Si
Al
U(Al,Si) 3 (a moy = 4.16 Å 43 at% Si)
+ UMo 2 Al 20
U(Al,Si) 3 (a moy = 4.17 Å 39 at% Si)
+ U 3 (Si,Al) 5
20
10
γU-Mo7 + traces (UC…)
0
0 50 100 150 200
Vertical position (µm)
Figure 6 : µ-XRD analysis of an U-Mo7/Al-Si7 diffusion couple.
(a) Major phases distribution throughout the IL, (b) simplified summary of the results
In U-Mo7/Al-Si5 couples, type 2 areas, with thinner U(Al,Si) 3 + U 3 (Si,Al) 5 sub-layers, were
also characterized by µ-XRD. No destabilisation of γU-Mo was evidenced beneath these
areas, contrary to that observed in U-Mo, by Komar et al, beneath locally thicker IL areas, in
U-Mo7/Al 6061 diffusion couples [14].
By comparing the results obtained on diffusion couples annealed at 450°C with those
concerning couples which underwent a complementary long annealing at 350°C, we have
checked that no significant evolution occurred in both types of ILs, apart an increase of the
grain size of the phases, despite of a massive destabilisation of the underlying γU-Mo7 alloy
(as expected, by reference to TTT curves [15]).
153 of 455